A conventional lancet will be described with reference to FIG. 13. A disposal puncture needle 127 is attached to a lancet 120, and a fingertip or arm of a patient is punctured with a needle 127A provided at the front end of the puncture needle 127 to collect blood from the punctured portion. The typical lancet 120 comprises a cylindrical body 121, and a cap 126. A slidable puncture rod 123 for holding the puncture needle 127 is incorporated in the body 121, and the puncture rod 123 has a first spring 122 for projecting the attached puncture needle 127, a second spring 124 for backing off the projected puncture needle 127, and a launch button 125 for releasing the compressed first spring 122.
The lancet 120 is used as follows. Initially, the cap 126 is removed from the body 121, and the puncture needle 127, from which a protection cap 127B is twisted and removed, is attached to the puncture rod 123 incorporated in the body, and the cap 126 is again put on the body. Then, the first spring 122 is compressed to set the lancet 120 in a state where puncture is possible (puncture-ready state), and a puncture target pressing surface 126A of the cap 126 is applied to a target to be punctured, such as a fingertip. When the launch button 125 is pressed, the puncture rod 123 slides, and simultaneously, the puncture needle 127 attached to a holder 123A also slides, and the puncture needle 127 hits the inner wall of the cap 126. At this time, the tip of the needle 127A slightly protrudes from a puncture hole 126B, and punctures the fingertip or the like. Thereafter, the puncture needle 127 is immediately removed from the fingertip or the like by the second spring 124. Thereby, the lancet 122 collects blood. (Refer to Japanese Published Patent Application No. 2000-237172 (Pages 3 and 4, FIG. 1).)
In the conventional lancet, however, in order to execute the puncture operation, initially the puncture needle housed in the blood collection device (lancet) is once held at a position where the first spring is charged and then released, whereby the puncture needle is displaced in the puncture direction, i.e., it moves toward a body region to be punctured. After the puncture needle hits the lancet body, the puncture needle is backed off to the initial position by the function of the second spring, and stopped. According to this method, shock, sound, and vibration during puncture are considerable. Further, since the puncture needle vibrates due to the balance of the spring forces, the puncture needle might puncture the same portion or its vicinity a few times. Further, when attaching or detaching the puncture needle to/from the lancet, the needle is unprotected because it is not covered with the protection cap, and the puncture rod easily moves because it is held by only the spring, leading to puncture by mistake.